title: Light-mediated polarization of the PIN3 auxin transporter for the phototropic response in Arabidopsis.
abstract: Phototropism is an adaptation response, through which plants grow towards the light. It involves light perception and asymmetric distribution of the plant hormone auxin. Here we identify a crucial part of the mechanism for phototropism, revealing how light perception initiates auxin redistribution that leads to directional growth. We show that light polarizes the cellular localization of the auxin efflux carrier PIN3 in hypocotyl endodermis cells, resulting in changes in auxin distribution and differential growth. In the dark, high expression and activity of the PINOID (PID) kinase correlates with apolar targeting of PIN3 to all cell sides. Following illumination, light represses PINOID transcription and PIN3 is polarized specifically to the inner cell sides by GNOM ARF GTPase GEF (guanine nucleotide exchange factor)-dependent trafficking. Thus, differential trafficking at the shaded and illuminated hypocotyl side aligns PIN3 polarity with the light direction, and presumably redirects auxin flow towards the shaded side, where auxin promotes growth, causing hypocotyls to bend towards the light. Our results imply that PID phosphorylation-dependent recruitment of PIN proteins into distinct trafficking pathways is a mechanism to polarize auxin fluxes in response to different environmental and endogenous cues.
authors.affiliation: Department of Plant Systems Biology, VIB, Universiteit Gent, Technologiepark 927, B-9052 Gent, Belgium.
authors.forename: Zhaojun
authors.initials: Z
authors.lastname: Ding
authors.forename: Carlos S
authors.initials: CS
authors.lastname: Galván-Ampudia
authors.forename: Emilie
authors.initials: E
authors.lastname: Demarsy
authors.forename: Łukasz
authors.initials: Ł
authors.lastname: Łangowski
authors.forename: Jürgen
authors.initials: J
authors.lastname: Kleine-Vehn
authors.forename: Yuanwei
authors.initials: Y
authors.lastname: Fan
authors.forename: Miyo T
authors.initials: MT
authors.lastname: Morita
authors.forename: Masao
authors.initials: M
authors.lastname: Tasaka
authors.forename: Christian
authors.initials: C
authors.lastname: Fankhauser
authors.forename: Remko
authors.initials: R
authors.lastname: Offringa
authors.forename: Jiří
authors.initials: J
authors.lastname: Friml
mesh_terms: D017360:Arabidopsis / Q000166:cytology / Q000378:metabolism* / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D016764:Cell Polarity; D018546:Hypocotyl / Q000254:growth & development / Q000378:metabolism; D007210:Indoleacetic Acids / Q000378:metabolism*; D008027:Light; D018524:Phototropism / Q000502:physiology*; D021381:Protein Transport; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; D007210:Indoleacetic Acids; C449300:PIN3 protein, Arabidopsis; D011993:Recombinant Fusion Proteins